I really wanted to like this book. After all, the basic plot (character awakes in strange circumstances on a vast starship, and must undertake a long journey with many challenges in order to discover why) is a classic. I doubt that I'm the only reader of space fiction who has dreamed about such a quest, and even thought about writing it.... But I digress. Just because a story is based on a timeless theme doesn't mean it's no good, does it?
So the narrative arc is familiar, the characters equally so, the vaguely horrific quest works well, and the overall resolution is nicely judged. So why Do I give this book only three stars? Other reviewers have already identified the book's fatal weakness: the descriptions. Descriptions of characters and of monsters, both human and monstrous. Descriptions of the ship: its processes, systems, structures, spaces and spatial elements. Descriptions of the forces that act upon the characters, including sounds, accelerations, temperatures... The author insists on painting a detailed picture of every move, every event, every spin-up and chill-down, and then finds himself running out of adjectives. The result is often repetitive, and unfortunately flat.
As I said, I've read many science fiction stories in which the writers strove to describe huge alien forms and to hint at experiences beyond human ken. And generally they succeeded. I have a feeling that what's happening here is that the author has watched too many science fiction moves. When computer graphics can casually fill the screen with aliens, or a starship the size of a small planet, or an attack by thousands of robots, two things can happen to a writer. First, s/he may believe that anything less will not satisfy the reader, and s/he will strive to compete with the visual medium. Second, s/he may hope that the book can become the basis for a successful movie, and drifts into writing not a novel but a screenplay with detailed instructions to the special effects team.
How close does Greg Bear come to these tendencies - the Scylla and Charybdis of CGI envy? A bit too close for comfort, I'm afraid.